The Iran-Iraq War began on 22 September 1980, when Iraqi forces under Saddam Hussein launched a full-scale invasion of western Iran, and ended on 20 August 1988 with the implementation of a ceasefire under UN Security Council Resolution 598 (adopted 20 July 1987).
Iraq's stated grievances centered on the Shatt al-Arab waterway, whose boundary had been set along the thalweg by the 1975 Algiers Agreement between Saddam Hussein and the Shah. Baghdad abrogated that agreement days before the invasion. Underlying motives included Saddam's fear that Ayatollah Khomeini's 1979 Islamic Revolution would inspire Iraq's Shia majority, and ambitions to assert regional primacy while Iran was diplomatically isolated and its military purged.
The war passed through several phases: an initial Iraqi advance into Khuzestan; an Iranian counter-offensive that recaptured Khorramshahr in May 1982; years of attritional trench warfare reminiscent of the Western Front; the "War of the Cities" featuring missile strikes on urban centers; and the "Tanker War" in the Persian Gulf, which drew in U.S. naval forces under Operation Earnest Will from 1987. Iraq used chemical weapons extensively, including against Iranian troops and against Iraqi Kurds — most notoriously at Halabja in March 1988.
Estimated casualties range widely; most scholars cite several hundred thousand dead on each side, with Iranian losses generally considered higher. Economic costs exceeded an estimated $1 trillion combined.
Externally, Iraq received financial backing from Gulf Arab states (notably Saudi Arabia and Kuwait), arms from the Soviet Union and France, and intelligence and dual-use exports from the United States, even as Washington also covertly sold arms to Iran in the Iran-Contra affair. The war reshaped Gulf security: it militarized the waterways, accelerated GCC cooperation (the Gulf Cooperation Council was founded in 1981), left Iraq heavily indebted to Kuwait — a grievance feeding the 1990 invasion of Kuwait — and entrenched Iran's distrust of the international system, which had not condemned Iraq's chemical weapons use.
Example
In March 1988, Iraqi forces dropped chemical weapons on the Kurdish town of Halabja during the final year of the Iran-Iraq War, killing an estimated 5,000 civilians.
Frequently asked questions
Iraq initiated the war by invading Iran on 22 September 1980. A 1991 UN report by Secretary-General Javier Pérez de Cuéllar identified Iraq's attack as the act that began the conflict.
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